ATI
Model Q45CT Portable Transmitter
Part 5
– Calibration
28
O&M Manual
Rev-G (7/15)
5.12 Zero Cal Calibration Explained
The sensor offset must be set for the system only on initial sensor
installation, or when the cable length has been altered. The Zero Cal
method establishes all of the sensor offset points for the instrument’s 6
ranges of operation.
5.2
Performing a 1-Point Calibration
This calibration method is intended to be used as an on-line calibration method
or a wet-cal with reference solutions. During calibration, the system will display
the current conductivity reading, and the user can manually enter a reference
value from a reference solution bottle or a comparative reference instrument.
For wet calibrations, the user may use pre-made calibration references (also
available from ATI) or a NaCl solution may be made using pure, dried NaCl
crystals and one liter of high purity, de-ionized, CO
2
-free water as mixed in the
table shown in Figure 7. All table data is at 25°C - therefore, the sensor must be
at this temperature to calibrate properly using the table data. If another reference
calibration solution is being used, be sure to note temperature of reference
solution before calibration. Since the sensor must ideally be at the specified
temperature, wet calibrations can be difficult to perform accurately.
NaCl Reference Solution for
Calibration (25°C)
μS/cm
NaCl (gm)
100
0.05
200
0.10
500
0.25
1000
0.50
2000
1.01
3000
1.53
4000
2.06
5000
2.61
8000
4.34
10000
5.56
20000
11.59
Figure 7 - NaCl Reference Solution for Calibration
